Spaced plate circuit interrupter



March 25, 1952 J. A. KALAWAY SPACED PLATE CIRCUIT INTERRUPTER Filed July5, 1947 INVENTOR Joli/2 f]. Kala way."

BY GYM 9-/ ATTORNEY Patented Mar. 25, 1952 SPACED PLATE CIRCUITINTERRUPTER John A. Kalaway, Turtle Creek, Pa., assignor to WestinghouseElectric burgh Corporation, East Pitts- Pa., a corporation ofPennsylvania Application July 5, 1947, Serial No. 759,270

2 Claims. 1

This invention relates to circuit interrupters, in general, and moreparticularly to arc extinguishing structures therefor.

A general object of my invention is to provide an improved circuitinterrupter of the spaced metallic plate type in which the arc is morereadily moved into engagement with the several plates and therebetweento more rapidly eifect its interruption.

A more specific object of my invention is to provide an improved circuitinterrupter of the spaced magnetic plate type in which the venting meansis so improved as to facilitate the entry of the are between the platesand to minimize the back pressure of gases formed by the arc.

Still a further object is to improve the venting arrangement of an arcextinguishing structure of the foregoing type by symmetrically providingventing passages in such a manner that the length of the arc travel uponthe several plates is not impaired.

Further objects and advantages will readily become apparent upon readingthe following specification, taken in conjunction with the drawing, inwhich:

Figure l is a side elevational view, partially in section, of a S-pcleair break circuit interrupter embodying my invention and shown in theopen circuit position;

Fig. 2 is a plan view of one of the slotted ma netic plates used in theextinguisher of Fig. 1;

Fig. 3 is a side elevational view of the plate shown in Fig. 2;

Fig. 4 is a plan view of the arc extinguishing structure of Figure 1,indicating the alignment of the notches provided in the several platesto provide venting passages along the rear of the extinguisher; and

Fig. 5 is an exploded view of several of the spaced magnetic plates tomore clearly show the alignment of the notches provided in the platestructure.

Referring to the drawing, and more particularly to Fig. 1 thereof, thereference numeral I generally designates a 3-pole air break type ofcircuit interrupter to interrupt the three phases of the protectedcircuit. All three poles of the breaker are simultaneously opened by theactuation of an operating handle 2 which projects through a slot 3 inthe cover 4 of the circuit breaker I. The cover 4 is mounted upon thebase 5 of the interrupter I.

Considering one pole of the interrupter along one side thereof, theextinguishing structure of which is broken away to indicate the methodof are rupture, it will be observed that a line terminal 6 is providedadacent one end of the breaker I. The line terminal 6 is electricallyconnected by a suitable configured strap I to a stationary contact 8,which, in the closed circuit position of the interrupter makeselectrical engagement with the movable contact I0 of the interrupter.Preferably, the movable contact I0 is fixedly secured to a rotatablemovable contact arm I I actuated by any suitable fast operatingmechanism generally designated by the reference numeral I2. Themechanism I2 forms no part of my invention and may be of any desiredconventional type. It sufiices to say the mechanism I2 actuated byoperation of the handle 2 serves to simultaneously open the three polesof the interrupter I to break the three phases of the protected circuit.

Electrically connected to the conducting con tact arm II is a conductingshunt I3 which makes electrical connection to a strap conductor I4, thelatter leading to the left-hand line terminal I5 of the interrupter. Asis well known by those skilled in the art, a suitable trip mechanism maybe interposed in the circuit to effect opening of the interrupter I inresponse to excessive current conditions in the protected circuit. Thebase 5 and the cover 4 are preferably formed of a suitably moldedmaterial such as Bakelite or the like.

During the opening operation, the upward separation of the movablecontact I0 away from the stationary contact 8 establishes an arc, theinitial position of which is designated by the dotted line 9. This are 9is extinguished by the operation of an arc extinguishing structuregenerally designated by the reference numeral I6, and consisting of aplurality of spaced slotted magnetic plates H, the configuration of eachof which is more clearly indicated in Figures 2 and 3. As shown in thesefigures, each plate I 1 is preferably formed of magnetic material, inthis instance, soft sheet steel. Each plate I! has a converging slot I8extending inwardly from one side I9 of the plate. Lugs 20 are preferablyintegrally formed with the plate I! to permit its rigid attachmentwithin a curved U-shaped fiber wrapper or enclosure designated by thereference numeral 2| and shown more clearly in Fig. 4. The fiber wrapperor enclosure 2| is made of fiber sheet material and is provided with aplurality of slots 22 through which project the lugs 20 of the platesII. After the several plates I! have been suitably positioned with theirlugs 29 extending through the slots 22 of the fiber wrapper 2|, at leastsome of the lugs 2|) are swaged over to maintain the wrapper 2| and theseveral plates I! together as a unit which forms a subassembly and isdesignated by the reference numeral 23 of Fig. 4. A steel arc runner 24shown more clearly in Figs. 1 and 4 also has side lugs 20 which alsoproject through suitable slots provided in the side walls of the fiberwrapperil. Preferably, the arc runner 26 has a reverse bend at its lefthand end, as indicated at 25, within which is positioned a plate 28provided with a threaded aperture 27.

To maintain the extinguisher it in position relative to the circuitinterrupter it is only necessary to provide a screw 28, the upper end ofwhich, as viewed in Figure 1, is threadedly secured into the threadedaperture 2? of the arc runner 24. This serves to rigidly fasten thesub-assembly 23 fixedly in position, and yet permits the ready removalthereof upon unscrewing the screw 28 from the arc runer 24.

The are 9 which is initially established upon the separation of themovable contact It upwardly away from the stationary contact 8, is drawnmagnetically toward the apex of the several slots it provided in themagnetic plates H, as indicated by the arrow 29 of Fig. 4. When the are9 reaches the closed ends of the several slots I8, it is subdivided intoa plurality of serially related arcs designated by the reference numeral30 in Fig. 1. These short serially related arcs 3|! continue to movetoward the magnetic centers of-the plates I? as indicated by the arrow 3in Fig. 4. r The increased are voltage due to the drop across thevarious cathode and anode terminals and the cooling and neutralizing ofthe hot ionized arc gas by the steel plates H extinguishes the are.

We have found that the presence of the several serially related arcs 39adjacent to the fiber wrapper 2!, together with the heated air, tends toprovide a back pressure of gas which inhibits the rapid movement of theshort arcs 38 between the magnetic plates 11. It is desirable to keepthe arc extinguisher It as small as possible to provide small dimensionsfor the interrupter It is also necessary to maintain adequate clearancebetween'the extinguisher it of one pole and the extinguisher it of theadjacently disposed pole. Furthermore, it is necessary to provideadequate length-of arc travel A between the plates as indicated in Fig.4. This is necessary .so that the arcs 30 will not heat any particularportions of the plates I! but are kept rapidly moving until interruptionfollows. Thus the length of travel A is important to provide V properarc travel.

The provision of a space between each of the symmetrical positioning ofthe venting passages 33, however formed, the arcs 30 are not acted uponby unbalanced back gas pressures and are not deviated thereby from theirstraight line course as defined by the arrow 3| of Fig. 4. Furthermore,the notches 32, being at the sides of the center axis of the plates, donot shorten the amount of sheet plate material available to permit fulllength of arc travel along the center axis of the plates beforeinterruption ensues. Another feature of this are extinguisher is thatthere are no openings through the plates adjacent the path of arcmovement so that the maximum number of short arcs is maintained between.the plates, with the maximum number of cathode and anode drops and themaximum arc voltage.

I have found upon testing my improved arc extinguisher l6 that shortcircuit currents of 10,000 amperes and over may be successfullyinterrupted on voltages up to 250 volts direct current or \600' voltsalternating current in a very small space. Without the vent passages 33,it was found that back-pressure of the gases formed by the heated airand also by gas evolved from the fiber wrapper 2| prevented the rapidmovement of the several arcs 30 along the magnetic plates I! in thedirection of the arrow 3| of Fig. 7

4 and hampered interruption of the arc.

From the foregoing description of my improved extinguisher, it will beapparent that the symmetrical venting arrangement provides an arcextinguishing structure 16 of minimum dimensions without impairing thedesired high speed are movement between the plates H. The two ventingpassages 33 provided upon alignment of the several notches 32 readilypermit venting of the arc gases and direct them upwardly, as viewed Fig.1, away from the separated contact structure to minimize the possibilityof restriking. The venting passages 33 prevent the are 9 from beingblown back by the back-pressure of the gases formed and permitting it torestrike between the contacts 8, l0.

Although I have shown and described a particular structure, it is to beclearly understood that the same was merely for the purpose ofillustration, and that changes and modifications may readily-be madetherein by those skilled in the art without departing from the spiritand scope of the appended claims.

I claim as my invention:

1. A circuit interrupter including means for establishing an are, an arcextinguishing means for extinguishing the are including a plurality ofspaced conducting plates, each conducting plate having a single-endedslot extending inwardly from the front end of the plate and along thecentral axis thereof, an insulating enclosure substantially enclosingthe rear ends of the plates, each plate having a. pair of notchesprovided therein at the rear corners thereof, the several notchesaligning and cooperating with the insulating enclosure to define twocontinuousventing passages at the rear corners of the plates to minimizeback pressure of the formed are gases and to prevent unbalanced gaspressure forces, and the portions of the insulating enclosure whichbound on the two continuous passages being completely closed to confinethe arc gases within said continuous venting passages.

2. Arc-extinguishing means for a circuit interrupter including a stackof spaced conducting magnetic plates, each magnetic plate having asingle V-shaped slot extending inwardly from the front end thereo aninsulating enclosure 7 substantially enclosing the rear portion of thesides-and rear ends of the plates, each plate having a pair of notchesprovided therein at the rear corners thereof, the several notchesaligning and cooperating with the insulating enclosure to define twoventing passages extending continuously through the stack of plates atthe rear corners of the plates to minimize back pressure of the formedarc gases and to prevent unbalanced gas pressure forces, and thebounding portions of the insulating enclosure which bound on the twocontinuous passages being completely closed to confine the arc gaseswithin said continuous venting passages.

JOHN A. KALAWAY.

6 REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,868,442 Corbett July 19, 19322,030,582 Graves, Jr Feb. 11, 1936 2,134,565 Leonard Oct. 25, 19382,140,360 Jennings Dec. 13, 1938 2,244,061 Graves, Jr. June 3, 19412,416,164 Ellis et a1 Feb. 18, 1947

